Quantifying contributions of natural variability and anthropogenic forcings on increased fire weather risk over the western United States

Yizhou Zhuang, Rong Fu, Benjamin D. Santer, Robert E. Dickinson and Alex Hall
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Yizhou Zhuang: a Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095;
Rong Fu: a Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095;
Benjamin D. Santer: b Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Livermore, CA 94550
Robert E. Dickinson: a Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095;
Alex Hall: a Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095;

Proceedings of the National Academy of Sciences, 2021, vol. 118, issue 45, e2111875118

Abstract: The western United States (WUS) has experienced a rapid increase of fire weather (as indicated by vapor pressure deficit, VPD) in recent decades, especially in the warm season. However, the extent to which an increase of VPD is due to natural variability or anthropogenic warming has been unclear. Our observation-based estimate suggests ∼one-third of the VPD trend is attributable to natural variability of atmospheric circulation, whereas ∼two-thirds is explained by anthropogenic warming. In addition, climate models attribute ∼90% of the VPD trend to anthropogenic warming. Both estimates suggest that anthropogenic warming is the main cause for increasing fire weather and provide a likely range for the true anthropogenic contribution to the WUS trend in VPD.

Keywords: western United States; fire weather; attribution; atmospheric circulation; anthropogenic warming (search for similar items in EconPapers)
Date: 2021
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